Oleamide (1, cis-9-octadecenamide) is a naturally occurring brain constituent that has been shown to accumulate and disappear under conditions of sleep deprivation and sleep recovery, respectively (Cravat et al., Science 1995, 268, 1506-1509; Lerner et al., Proc. Natl. Acad. Sci. U.S.A 1994, 91, 9505-9508; Cravatt et al., J. Am. Chem. Soc. 1996, 118, 580-590). In a structurally specific manner, 1 has been shown to induce physiological sleep in animals at nanomolar quantities when injected intravascularly (Cravat et al., Science 1995, 268, 1506-1509). Hydrolysis of 1 by an enzyme (oleamide hydrolase) present in the cell membrane rapidly degrades oleamide to oleic acid (cis-9-octadecenoic acid). In an effort to isolate a regulatory agent responsible for controlling endogenous concentrations of 1, an integral membrane protein, oleamide hydrolase, was found to catalyze the hydrolytic degradation of oleamide to give oleic acid (cis-9-octadecenoic acid) and ammonia (FIG. 3), neither of which demonstrate somnolescent activity (Cravat et al., Science 1995, 268, 1506-1509).
It has been found that oleamide hydrolase can be inhibited by phenylmethylsulfonyl fluoride, 4,4'-dithiodipyridine disulfide (a potent disulfide forming reagent), and HgCl.sub.2 (IC.sub.50 =700 nM, K.sub.i, app =37 nM), but not by 1 mM EDTA. This suggests that a thiol is intimately involved in the catalytic process and that the enzyme may be a cysteine amidase or possibly a serine amidase with an active site cysteine residue.
A variety of tight binding or irreversible inhibitors of serine and cysteine proteases have been described. These include irreversible inhibitors such as halomethyl ketones (Kettner et al., Biochemistry 1978, 17, 4778-4784; Kettner et al., Thromb. Res. 1979, 14, 969-973; C. Giordano, et al., Eur. J. Med. Chem. 1992, 27, 865-873; Rauber et al., Biochem. J. 1986, 239, 633-640; Angliker et al., Biochem. J. 1987, 241, 871-875), Michael acceptors (Hanzlik et al., J. Med. Chem. 1984, 27, 711-712), epoxides (C. Parkes, et al., Biochem. J. 1985, 230, 509-516), O-acyl hydroxylamines (Bromme et al., Biochem. J. 1989, 263, 861-866) and diazomethylketones (Green et al., J. Biol. Chem. 1981, 256, 1923-1928) as well as reversible transition state mimetic inhibitors such as ketones (Mehdi, S. Bioorg. Chem. 1993, 21, 249-259), aldehydes (Westerik et al., J. Biol. Chem. 1972, 247, 8195-8197), cyclopropenones (Ando et al., J. Am. Chem. Soc. 1993, 115, 1174-1175) and electron-deficient carbonyl compounds such as trifluoromethyl ketones (Wolfenden et al., Annu. Rev. Biophys. Bioeng. 1976, 5, 271; Gelb et al., Biochemistry 1985, 24, 1813-1817; Imperiali et al., Biochemistry 1986, 25, 3760-376; Koutek et al., J. Biol. Chem. 1994, 269, 22937-22940), .alpha.-keto acid derivatives (Li, Z. et al., J. Med. Chem. 1993, 36, 3472-3480; Harbeson et al., J. Med. Chem. 1994, 37, 2918-2929; Peet et al., J. Med. Chem. 1990, 33, 394-407; Angelastro et al., J. Med. Chem. 1990, 33, 11-13) and tricarbonyl compounds (Wasserman et al., J. Org. Chem. 1993, 58, 4785-4787).
On the other hand, only one possibly specific inhibitor of oleamide hydrolase has been reported (IC.sub.50 =3 .mu.M at [S]=0.26 K.sub.m) (Maurelli et al., FEBS Lett. 1995, 377, 82-86) and only one report of an investigation of inhibitors of related fatty acid amidases has been disclosed to date (Koutek et al., J. Biol. Chem. 1994, 269, 22937-22940).
What is needed are highly potent inhibitors of oleamide hydrolase for inhibiting the hydrolysis of oleamide and agonists of oleamide induced sleep.